Field of the Invention
The present invention relates to a motor speed control device, primarily for electric and hybrid vehicles.
A variety of motor speed control systems have been developed in the art. A major problem with these conventional systems is the difficulty of heat control and the cost of this equipment. When a vehicle climbs a steep grade, motor controllers been to heat up rapidly under the load and soon start to limit the power to the motor. The motor in a conventional electric vehicle operates by transferring power from the batteries in the form of Counter Electromotive Force. The amount of current flow is determined by the amount of resistance in the circuit or the load placed on the motor. Therefore, current flow has to be as much as four times the running current. This high current load must be carried by the motor speed controller. Generally, these are of MOSFET or Transistor design. Frequent starting or running of the motor at these high current flows causes these components to overheat and create an excessive drain on the batteries.
In addition, the varying rates at which the motor in these vehicles must rotate severely limits the range of travel of these vehicles. Conventional motor speed controllers, transmissions or gear-boxes do not solve this problem.
U.S. Pat. No. 1,392,276 discloses a reduction gear for a propeller to achieve slower propeller rotation than motor rotation. The speed reduction was achieved by engagement of a series of different diameter, discontinuous gears.
U.S. Pat. No. 4,173,155 discloses a variable diameter torque sensing drive aimed at extension of the life of V-belts in the transmission mechanisms of harvester combines. These belts were known to slip as sudden increased loads were placed on the harvester, resulting in premature destruction of the V-belts. The torque sensor comprised a set of "sheaves" of variable diameter which prevent slippage of the V-belts. In addition, a dual speed gear case assembly was described for use in connection with the variable diameter torque sensor wherein an operator could shift a driven gear in either a forward or rearward direction to engage with a different diameter drive gear.
U.S. Pat. No. 4,173,156 discloses an infinitely variable cone pulley gear in which torque is transmitted via an oil cushion intermediate a driving and a driven element to provide for a torque dependent oil pressure circuit.
U.S. Pat. No. 4,427,930 discloses an electric vehicle current regulator which provides a method for obtaining correspondence between the accelerator pedal displacement and motor speed of the electric vehicle.
U.S. Pat. No. 4,427,931 discloses a speed control apparatus for a direct current motor to achieve reduced energy consumption by a direct current motor in which a bridge circuit is used to eliminate unnecessary power consumption.
U.S. Pat. No. 5,067,360 discloses a toroidal continuously variable transmission comprising coaxial toric input and output elements.
U.S. Pat. No. 5,067,361 discloses a transmission series in which the center distances and transmission ratios of variation stages within the series are coordinated such that a reduction in the number of different gearwheels needed for use with different motors is reduced.
U.S. Pat. No. 5,067,372 discloses a control system for a continuously variable transmission comprising a hydrokinetic torque transmitting unit. The transmission ratio is varied by varying the contact radii of axially displaceable conical disks in contact with a V-belt.
U.S. Pat. No. 5,318,486 discloses a driving hub for a bicycle having an infinitely adjustable transmission ratio comprising a ball friction gear.
U.S. Pat. No. 5,381,704 discloses a bearing tooth gear in which rotative forces are transmitted through a series of meshed gears in which the sliding contact of conventional gear teeth is replaced with the rolling contact of rotatable bearings that contact corresponding teeth of an adjacent gear, with the axes of the two gears being variable over a wide range of angles relative to each other. One set of teeth are of conical shape to provide contact through the entire driving stroke.
U.S. Pat. No. 5,403,241 discloses an infinitely variable hydrostatic mechanical power shift gearbox in which a multi-shaft toothed-wheel planetary gearing achieves commensurate increases or decreases in the speed of rotation of input and output shafts.
U.S. Pat. No. 5,403,244 discloses an electric vehicle drive train with a transmission comprising a single stage planetary gearbox, operable either in a speed reduction mode at low speed, high torque requirement starting situations, and in a direct coupled mode in high speed, low torque requirement situations. The transmission requires at least momentary decoupling from the motor when operation is switched from the discontinuous speed reduction mode to the direct coupled mode. This also requires changes in the speed of rotation of the driving motor.
U.S. Pat. No. 5,406,483 discloses an engine having a variable transmission control system in which an electronically controlled powershift to avoid jolts during gearshifts. This enables extraction of maximum engine power from the engine operating at any given speed.
In none of the foregoing patents has a speed control device been identified in which a cone-shaped drive gear and an intermeshed driven gear provide for a constantly variable ratio between engine speed and torque upon demand such that a drive motor may operate at a constant speed while allowing various speeds to be transmitted to the driving wheels of the vehicle.